Exploration as an idiom: foray vs forage [closed]

I know one of either "foray" vs "forage" is used idiomatically, to mean "to explore something new/exciting". It has adventurous connotations.

It would be an interesting foray into the underlying truths.

It would certainly be an interesting forage of the underpinning truths.

What is the correct word, and what is the most common expression of this idiom?

Foray has two related meanings. This may explain why any recourse to dictionaries has not entirely helped you.

Foray = "a short period of time being involved in an activity that is different from and outside the range of a usual set of activities"

It also means = "the act of an army suddenly and quickly entering the area belonging to the enemy in order to attack them or steal their supplies"

Cambridge dictionary

The first meaning relates to your first sentence, which reads clearly, correctly and unambiguously. The second meaning, although not strictly applicable to that sentence, gives it the adventurous overtones you mention.

To forage = to go from place to place searching for things that you can eat or use

Cambridge dictionary

Examples are: "The children had been living on the streets, foraging for scraps" and "The pigs foraged in the woods for acorns."

Although the emphasis of dictionary definitions is on finding food, this is not essential. For example, Meriam Webster and others have "to make a search".

Merriam Webster

So, you may forage for truths. "forage of" is not commonly used and "forage for" is a more conventional expression. In Ngram, the occurrence of forage of is about a tenth that of forage for.